The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art.
In traditional textile dyeing processes, large amounts of water are used as a dye solvent, resulting in one of the largest sources of water pollution for industrialized countries. Such dyeing processes often require various harmful chemicals and produce numerous harmful byproducts. In addition, traditional dyeing processes require large amounts of energy.
An alternative dye solvent to water is super critical carbon dioxide (sc-CO2). However, the use of sc-CO2 as a solvent has generally been limited to the dyeing of artificial fibers and has enjoyed only very limited application to natural fibers, such as cotton and wool. Sc—CO2 is a hydrophobic solvent, which does not swell hydrophilic cotton or wool fibers. Sc—CO2 is unable to break the hydrogen bonds between adjacent molecular chains to disrupt the structure of the natural fibers in order to facilitate the diffusion of the dye into the fibers. In addition, most commercial cotton dyes are salts, which are insoluble in sc-CO2 without the use of co-solvents. However, the use of co-solvents requires that the fabrics become saturated, thus requiring drying of the fabrics and more complex cleaning of the process chamber and dyeing components.
Nature has demonstrated alternative methods of producing colors that do not necessarily require the use of dyes. By arranging structures to manipulate light, different colors can be created through interference effects. For example, various moths and butterflies have photonic structures on a nano-scale that produce a multitude of mechanisms for producing various visual effects, including multilayer interference, diffraction, Bragg scattering, Tyndall scattering, and Rayleigh scattering to create colors. These structures can have multiple microstructures from the micron scale to nanometers arranged in various shapes and sizes separated by nanometer scale ridges and periodic airgaps. One example for selectively reflecting blue-green light is seen on the tropical butterfly Morphos.